LAST JUNE Secretary of State Colin L. Powell visited Sudan in an attempt to stop the Darfur genocide. Sudan's government rewarded him with promises to rein in its allies in the Janjaweed death squads; to stop impeding humanitarian access to Darfur; and to open political talks with Darfur's rebels. None of these concessions worked The upshot of Mr. Powell's visit was that mass killing continued, and Darfur's death toll is likely to be even more appalling this year than last.

This week it is the turn of Robert B. Zoellick, the new deputy at the State Department, to journey to Sudan. Mr. Zoellick is a forceful diplomat But success is unlikely unless the administration absorbs the lessons of the past year and changes its strategy. Diplomatic pressure, which should be aimed primarily at getting a large peacekeeping force into Darfur, won't work unless it's supported by the threat of sanctions. And neither the sanctions threat nor the peacekeeping deployment will be credible unless the United States invests more political capital in Darfur than it has so far.

After Mr. Powell's visit last year, the United Nations Security Council passed two resolutions threatening sanctions but then never followed through; this gave Sudan's rulers a green light to kill more people. The reason for the lack of follow-through was that the Bush administration made a conscious decision not to elevate Darfur's genocide to the top of its agenda. Mr. Bush did not place phone calls to the leaders of China and Russia to insist that they back tougher action

After Mr. Powell's visit, too, ground was prepared for a small peace-monitoring deployment under the umbrella of the African Union. The presence of AU forces helped to reduce violence but only to a limited extent; 2,000 or so troops cannot monitor an area the size of France The AU's leaders, notably the South Africans and the Nigerians, have been more interested in retaining a lead role in Darfur than in preventing genocide; they see their deployment as a sign that Africa can be responsible for its own problems, and they are reluctant to admit that a bigger deployment is needed

In a better world, the United States would not have to lead on Darfur. Russia and China would support sanctions without being pressured; the African Union would be less prickly France, in particular, would use its military clout in the region to support the AU peacekeepers. Instead, when NATO's secretary general suggested using his organization's assets to support the AU mission, France resisted, apparently out of a desire to preserve its own status as chief military intervener in Africa.

You face genocide in Sudan with the international partners you have, not the ones you might wish to have. If the United States does not lead on Darfur, nobody else is going to To achieve that objective, Mr. Zoellick needs to break the collective paralysis by changing the way the Chinese, Russians, Europeans and Africans think; his most important mission is not this week's visit to Khartoum but future trips to Beijing, Moscow and so on